On 2016-01-30, LÉVAI Dániel <[email protected]> wrote: > Hi! > > My ISP recently enabled ipv6 on their network, and started sending > router advertisements (offering a /64 prefix) on their pppoe end. So now > I have an autoconf'd v6 address on my pppoe0 device (yay!), and I wish > to set my in-home devices a v6 address each. > > The router that has the pppoe device also has three other interfaces: > re1, athn0, athn1. All of these are LAN. > > What I do now, is that I have rtadvd(8) running on these three > devices (re1, athn*). But I have no idea how to generate those > autoconfprivacy addresses for these interfaces, and rtadvd needs > something there to advertise, so what I also do (and what is probably > not a very good idea) is that I just chop the last group of the > autoconf'd address of the pppoe0 device, and assign each LAN interface > almost the same IPv6 address by changing the last group and incrementing > it (with the same /64 prefix of course). > > Although this works, and my in-home devices get IPv6 addresses from > rtadvd, each of them has this nice autoconfprivacy addresses. > > What I'm wondering about, is if I can assign my LAN interfaces (on my > router) autoconfprivacy addresses (for rtadvd(8)) that are derived from > the pppoe0 device's autoconf'd inet6 address. > > Does this make sense? Is this possible? > > > Daniel >
You aren't supposed to have addresses within the same /64 on more than one interface. The normal method is that you get an address for the PPP interface using SLAAC autoconf (as you have now), and request one or more *additional* /64s using DHCPv6-PD (prefix delegation) - one per interface. The DHCPv6 client assigns to "downstream" (client-facing) interfaces from this assignment, and you would use rtadvd to advertise the prefix (and possibly other information) to clients. There is no software in OpenBSD base to handle prefix delegation. I recommend "dhcpcd" from packages and I've added a pkg-readme with a minimal setup to handle just this (it is also a full-featured DHCP client for v4, but I'm personally only using it for v6). Unlike some alternatives it is actively maintained upstream by a responsive developer. This all assumes you are doing PPP (as you have described). The normal ISP setup for this is documented in Broadband Forum TR-187. In some cases people will only have an ISP-provided router and they don't have a way to request additional prefixes. If you see list posts with crazy schemes like "bridging ipv6 and routing ipv4" (like in some misc posts) that's because they are stuck with such a setup and their options are greatly reduced.
